A Self‐Standing and Flexible Electrode of Yolk–Shell CoS₂ Spheres Encapsulated with Nitrogen‐Doped Graphene for High‐Performance Lithium‐Ion Batteries

Abstract

Flexible lithium-ion batteries (LIBs) have recently attracted increasing attention with the fast development of bendable electronic systems. Herein, a facile and template-free solvothermal method is presented for the fabrication of hybrid yolk-shell CoS2 and nitrogen-doped graphene (NG) sheets. The yolk-shell architecture of CoS2 encapsulated with NG coating is designed for the dual protection of CoS2 to address the structural and interfacial stability concerns facing the CoS2 anode. The as-prepared composite can be assembled into a film, which can be used as a binder-free and flexible electrode for LIBs that does not require any carbon black conducting additives or current collectors. When evaluating lithium-storage properties, such a flexible electrode exhibits a high specific capacity of 992 mAh g(-1) in the first reversible discharge capacity at a current rate of 100 mA g(-1) and high reversible capacity of 882 mAh g(-1) after 150 cycles with excellent capacity retention of 89.91%. Furthermore, a reversible capacity as high as 655 mAh g(-1) is still achieved after 50 cycles even at a high rate of 5 C due to the yolk-shell structure and NG coating, which not only provide short Li-ion and electron pathways, but also accommodate large volume variation.

Self-assembled CoS2 nanoparticles wrapped by CoS2-quantum-dots-anchored graphene nanosheets as superior-capability anode for lithium-ion batteries

“…3a, three reduction peaks at 0.66, 1.25 and 1.79 V in the first cycle are observed. The peaks at 0.66 V is related to the formation of solid electrolyte interface (SEI) film [28]. However, the reduction peaks at 0.97, 1.3 and 1.8 V can be detected in the subsequent cycles.…”

Three-dimensional VS4/graphene hierarchical architecture as high-capacity anode for lithium-ion batteries

“…[16][17][18] These properties also become necessary for the electrode material of LIBs. Many studies have reported the manufacture of functional materials combined with graphene to get a good performance, such as V 2 O 5 /graphene [19], CoS 2 /graphene [20] and Si/graphene [21]. These materials exhibited excellent electrochemical performance due to the great characteristics of graphene [23] and CoS 2 [9], respectively.…”

Porous carbon-wrapped mesoporous Co9S8 fibers as stable anode for Li-Ion Batteries

“…[9][10][11] To obtain the enhanced specific capacity and good cyclic stability of electrode materials, one effective method is to construct appropriate nanostructures, [12][13][14] because nanostructured materials can resist the stress and accommodate the large volume variation during Li + insertion/desertion, leading to excellent cycling properties. [15,16] Thus, many attempts have been made in the past, such as, twodimensional mesoporous cobalt sulfides nanosheets, [17] three-dimensional rose-like Co 9 S 8 hierarchical architectures, [18] and yolk-shell microspheres of CoS 2 , [19] have shown improved electrochemical performances. Another attractive approach to 4 achieve anode materials with enhanced specific capacity and good cyclic stability is the design of cobalt sulfides/carbon hybrid materials, which is effective to prevent the aggregation and volume change during the electrochemical reactions.…”